“NEPR Showcase”? Showcase is obvious enough. But NEPR? It stands for New England Portfolio Reviews. Every year the Photographic Resource Center at Boston University and the Griffin Museum of Photography, in Winchester, jointly offer photographers in the region a chance to have their work critiqued by experts in the field. The six photographers with work in “NEPR Showcase,” which runs at the PRC through Aug. 25, were chosen from participants in at least one review who then presented their work at a portfolio walk in May.

Whether by design or chance, the work in the show neatly divides in two. Three photographers offer images primarily concerned with the external world (in fact, all three selections of photographs specifically relate to the man-made world), and three photographers have work primarily concerned with an internal world of emotion expressed and states of mind captured.

Philip Jones takes black-and-white photographs of urban structures or sites at night: the Tobin Bridge, Times Square, the Unisphere in New York’s Flushing Meadow, and so on. The images are cool, pristine, and extremely handsome, with a slight air of mystery. Both the handsomeness and the mystery owe a great deal to the pearliness of Jones’s light. It’s almost as if the shutter has clicked just as the bridge or underpass or whatever has exhaled.

Conversely, Shaun O’Boyle photographs landscapes that have stopped breathing: disused rail sidings, abandoned mill buildings, and the like. “A recurring experience during this project,” O’Boyle writes, “is seeing things left by previous generations — old buildings, structures, old walls, mounds on the landscape — without stories attached to explain them.” Certainly, no explanation is needed for an image as beautiful as “Green Mill, Monroe, MA.” Its combination of delicacy and strength informs all eight of O’Boyle’s photographs in the show, but none of the others have this ravishing verdigris look.

David Ricci also shoots in color, but the colors in the four photographs from his “Edge of Chaos” series look very different from O’Boyle’s subdued, slightly melancholy palette. They’re clear, bright, assertive. They have to be, to hold their own against and do justice to the demolition sites and junk piles he photographs. “Lawnmower,” for example, looks like an explosion in a rust factory — quite a magnificent explosion, too.

Rust, or oxidation, is a chemical reaction: metallic evidence of time’s passing. What concerns David Torcoletti in his “Soldiers” series is time as it affects — or erodes — memory. During the Vietnam War, a South Vietnamese radio announcer named Mai Lan would ask US soldiers and Marines to send her pictures of themselves. Three decades later, she showed Torcoletti a box of the photographs. Taken with cheap cameras like Instamatics and Swingers, the images hadn’t fared so well. Torcoletti realized that their deterioration granted them a larger significance. “They were now less specific to the individuals depicted,” he writes, “and more about war and hope and a peculiar distant ‘love’ that sustained these men in impossible circumstances.” The eight color images in this show are photographs he took of the originals — a memory of a memory of a memory, if you will.

David Ricci’s “Lawnmower” is part of his “Edge of Chaos” series.

The distance in time that informs “Soldiers” helps define the two photographs from Anita Līcis-Ribak’s “Time Still” series — and distance in space helps define the eight photographs from her “Letters Between the (Coast) Lines” series. The former look more like etchings than photographs, while the latter are collages. Five of them feature feet, and all of them include an irregular field of red (a fabric of some kind?). Matted but unframed, all 10 images have a provisional quality that contrasts with the work of the final photographer in the show, Beth Hankes. Her installation, “Unrelenting Silence,” consists of two dozen black-and-white photographs of a naked couple coupling (though discreetly so). The images, blurry and overlapping, conjoin at odd angles to form a single whole that’s a little bit like one of David Hockney’s Polaroid assemblages, from the ’80s. Like Ricci’s “Lawnmower,” “Unrelenting Silence” is a bit of an explosion, too, but with no visible rust.

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